1. Field of the Invention
The present invention relates to a method for forming a low-k dielectric layer for a semiconductor device. More particularly, the present invention relates to a method for forming a ternary silicon boron nitride (SiBN) layer having a low dielectric constant using an atomic layer deposition (ALD) process.
2. Description of the Related Art
Conventionally, a silicon nitride layer (SiNx) has been widely used in the manufacturing of semiconductor devices for several reasons. First, a SiNx layer has a high etching selectivity over a silicon oxide (SiO2) layer in a reactive ion etching (RIE) process and a wet etching process. Second, a SiNx layer exhibits strong oxidation and abrasion resistances. Third, a SiNx layer has an excellent diffusion barrier characteristic. However, a SiNx layer has a high dielectric constant of about 7. This high dielectric constant causes a propagation delay since parasitic capacitance increases as a chip size is reduced.
Recently, in view of the above disadvantage of a SiNx layer, the SiNx layer has been replaced with a boron nitride (BN) layer having a relatively low dielectric constant as a dielectric layer for a semiconductor device. The BN layer is formed by an ALD process at a low temperature in a range of 200° C. to 550° C., so that a conformal BN layer is formed.
The BN layer formed using the ALD process has a low dielectric constant, between 2.2 and 5 depending on deposition conditions, thereby reducing the propagation delay in comparison with a SiNx layer having a dielectric constant of about 7.
However, an ALD BN layer has several disadvantages. For example, an ALD BN layer is easily hydrolyzed by moisture in the atmosphere, is wet etched by a high temperature wet chemical based on sulfuric acid H2SO4, and has poor oxidation resistance.
Further, a conventional SiBN layer formed by a plasma enhanced chemical vapor deposition (PECVD) process has poor step coverage.